1. Field of the Invention:
The invention concerns a process control circuit for the control and monitoring of at least one metal-depositing bath, particularly, a gold bath.
2. Description of the Prior Art:
For the purpose of automatic analyses of liquid substances, it is obvious to use a program-controlled automatic analysis machine (German Offenlegungsschrift Nos. 2 341 149 or 2 113 854), consisting of a control device, a measuring stage and a regulating stage, as well as a dosing device. In the case of an analysis device for metal-depositing baths, it is necessary that the analysis of several parameters and/or components in a bath be carried out as rapidly as possible and, particularly, in the case of gold baths, with a high degree of precision. Thus, for example, in the case of a gold bath, the gold concentration level must be kept within a narrow range of a predetermined nominal value. The smaller this range, the more uniform the deposited layer becomes such that the consumption of the precious metal is optimally minimized. It is necessary to detect as measured quantities all the parameters which effect the function of the bath or baths. Parameters of this type are the pH-value, the concentration of the metal components in the bath fluids, as well as the temperature at the time of analysis. Also, the measuring electrode of a pH-value regulator degenerates in the course of time; i.e., it demonstrates a divergence vis-a-vis a calibration-buffer solution. In addition, in the case of a gold bath-analysis device with a colorimeter stage, it was determined that the windows of the colorimeter vessel become turbid as a result of condensation formation. Such turbidity leads to an erroneous result in a subsequent measurement. The pH-value regulator as well as the analyzer-section which determines the metal concentration, such as the gold bath analysis device, indirectly controls the influx of correction fluid to the bath. It is therefore important that the measured values be permitted to exhibit only a small deviation of .+-. 1%, at the most, from the actual values. The individual analyses must be capable of being carried out at as high a speed as possible, since only a repeated analysis of each of the baths makes it possible to maintain narrow ranges of individual bath temperatures to be measured and regulated.